Process and device for closing a tap hole

ABSTRACT

A process for closing a tap hole in a metallurgical vessel at least partially filled with a metal melt includes bringing a compressible fire-resistant material to the moth of a tubular closing element, providing a medium that substantially prevents contact between the fire resistant material and the metal melt, passing the closing element through the melt toward the bottom of the vessel, compressing the compressible material against the bottom of the vessel to form a seal between the outside of the closing element and the tap hole below the closing element, and moving a cut off device over the outside of the tap hole, thereby allowing the tap hole to be filled with a pourable refractory compound via the tubular closing element. A device for performing the process for closing a tap hole includes a tubular closing device with a groove at an end bottom facing the bottom of the metallurgical vessel. The open end of the groove also faces the bottom of the vessel and a closed end of the groove includes a compressible material. The sides of the groove are deflectable such that when the closing device is lowered onto the bottom of the vessel, the compressible material contacts the bottom of the vessel forming a seal.

BACKGROUND

1. Field of the Invention

The invention relates to a process for closing a tap hole in the bottomof a vessel filled with a metal melt, especially a vessel for a steelmelt, with a tubular closing element that is vertically movable towardand away from the entrance of the tap hole, and with a cut-off devicebelow the vessel bottom. The invention also relates to a device forimplementing a process for closing the tap hole.

2. Description of the Prior Art

The pool method for tapping a metallurgical vessel, especially a vesselfor steel, uses closing systems that allow a residue of metal melt andslag to be retained in the vessel. As a rule, such vessels are designedto be tiltable, so that the closing system is not exposed to wear fromthe molten metal or slag.

For example, reference DE 34 37 810 discloses a closing device for a taphole in the bottom of a metallurgical vessel, wherein a cut-off deviceis provided outside of and below the metallurgical vessel wherein thelower cut-off device can be moved against the tap hole from the outside.In the vessel interior, a tube is lowered from a release position intothe closing position. The mouth of the tube rests against the edge ofthe tap hole. When the tube is in the lowered, closing position,pourable filling material is passed through the tube into the tap hole.

It is further proposed in DE 34 37 810 that the tube be closed at thefoot end and that a gas be introduced into the interior to prevent themelt from entering the tube through the lower tube mouth.

In addition to experiencing high wear, the above closing device has thedisadvantage of low imperviousness. In rough steel mill operation,erosion occurs at the entrance of the tap hole. Furthermore, theaggressive slag and the high melt temperatures destroy the lower edge ofthe closing device irregularly.

SUMMARY OF THE INVENTION

The object of the invention is to create a process and a suitable devicefor repeatedly closing a tap hole of a metallurgical vessel which has ahigh overall useful life and ensures reliable cut-off without requiringthe vessel to be tilted as in the pool method.

The object is attained by a device for closing a tap hole in the bottomof a metallurgical vessel with a tubular closing element having a forkedgroove, the opening of which faces the vessel bottom. The blind end ofthe groove is filled with a compressible material and the remainder ofthe interior of the groove is fillable with a gas. The walls of thegroove includes a material which does not resist the pressing of theclosing element against the vessel bottom.

The object is further attained by a process for closing a tap hole inthe bottom of a metallurgical vessel including the steps of bringing acompressible fire-resistant material to the mouth of a closing element,providing a medium in front of the fire-resistant material in theclosing direction to substantially prevent contact between the fireresistant metal and the melt, passing the mouth of the closing elementthrough the melt and pressing the closing element against the vesselbottom with such force that the fire resistant material is compressed,and moving a cut-off device in front of the outside of the tap hole suchthat the tap hole is fillable with a pourable compound via the closingelement.

According to the invention, a compressible material is provided on theface of the closing element and, for the purpose of sealing, iscompressed during contact with the vessel bottom in the region of thetap hole.

During passage of the closing element through the melt, which hastemperatures between 1500 and 1700° C., the compressible sealingmaterial is protected against the effects of the melt and the moltenmetal. Thus, the compressible material used for sealing is afire-resistant material, and this material is introduced into a groovelocated on the face of the closing device, specifically, into the innerarea of the groove directed away from the mouth. The remaining interiorof the groove is left free and serves as a chamber for a gas thatprotects the sealing material during its passage through the melt.

This gas may originate from a solid or a liquid medium, which is appliedto the compressible material and gasified by heat. In a furtheradvantageous embodiment, the gas may be supplied continuously in theform of a gas; or, a gas may be used that expands due to heat during theresidence time of the compressible material in the melt bath (whichexperience has shown to be less than 30 seconds) and displaces the melt.The total volume of the gas is thereby sufficient to maintain thisprocess over the entire time.

The complete closing process is as follows: The tubular closing elementpasses through the slag and molten melt in the upright furnace until ittouches the vessel bottom and seals the latter tightly against anoutflow of the melt. At this time, the tap hole is still open, so thatthe melt and slag located in the interior of the tubular element and inthe tap hole exit the furnace vessel. After this, a cut-off device (aslider or flap) arranged outside of the vessel is closed. It is thenpossible to inspect the tap hole. This may be done by direct visualinspection or even by a camera or an endoscope. Furthermore, a tool maybe passed through the tubular closing element to treat the tap hole, forinstance, to remove skull. In addition, a device for repairing therefractory material, such as a gunning device, may be inserted throughthe tubular closing element into the tap hole. When the tap hole isfound to be usable, a pourable material is introduced into the tap holein a known manner. This protects the cut-off device and eases castingafter the cut-off is opened.

In an advantageous embodiment, the head of the closing element isdesigned as an exchangeable part. After one or more closing procedures,or needed, the exchangeable part is exchanged and equipped with a newsealing lip comprising the a groove and the compressible fire- resistantmaterial.

The exchangeable part may have a wall thickness clearly greater thanthat of the rest of the tubular closing element.

The walls of the groove protect the sealing material during the passagethrough the melt. When the sealing material, such for example, as ablanket or a formed piece made of fibers, has reached the bottom of themetallurgical vessel, the material of the groove walls should notinterfere with the compression of the sealing material. One suitablematerial would be a metal material, embodied in the form of acompensator. Further, a metal material that at least softens, melts orcarbonizes after passing through the melt in roughly 15 to 30 secondsmay also be used. Thus, a paperboard that has an adequate working lifeand carbonizes upon contact with the melt may be used.

It is further proposed that the base of the groove be designed to adjustto the conditions of the entrance of the tap hole. The face of theexchangeable part may thereby have a conical surface that peaks in thedirection of the center axis. However, the base of the groove may alsohave a shape corresponding to the entrance shape of the tap hole, sothat the thickness of the subsequently compressed sealing mass, i.e.,the fire-resistant fibers, remains virtually constant. In this way,especially high imperviousness is reliably achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the reference characters denote similarelements throughout the several views:

FIG. 1 is a sectional view of a metallurgical vessel showing twoembodiments of a closing element in accordance with the invention;

FIG. 2 is a sectional view of a metallurgical vessel showing two moreembodiments of a closing element in accordance with the invention; and

FIG. 3 is a sectional view showing two embodiments of an exchangeablepart of the closing element of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a section through part of a metallurgical vessel 10 with avessel mantle 11 and a refractory vessel lining 12. The vessel bottom 13includes a tap hole 14 whose mouth 16 is closed by a cut-off device 20,which is shown as a flap 21.

The tap hole 14 has a refractory lining 17, which may have a conicalslant in the region of the entrance 15.

A tubular closing element 31, on whose front face there is a groove 33,runs in the metallurgical vessel 10. The metallurgical vessel 10 may becovered by a lid 19. FIG. 1 shows two embodiments of closing element 31on the right and left sides of longitudinal axis I. A compressiblematerial F is introduced into a groove 34. In the embodiment shown onthe right side of the closing element 31, an exchangeable head 37 isattached to the main body 39 by a detachable connection 38.

In the embodiment shown on the side of the axis I, the closing element31 comprises a boring through which a gas G can be conveyed into thegroove interior 34 or the groove 33. In FIG. 1, the internal diameterd_(i) of the closing element 31 is equal to or greater than the diameterD_(i) of the tap hole 14. The ratio of d_(i) to D_(i) is preferably from0.7 to 2.0.

FIG. 2 shows a metallurgical vessel 10 filled with a metal melt M, onwhich slag S floats. The vessel 10 is covered by a lid 19, through whichthe main body 39 of the closing element 31 is run. The closing element31 is held by a bracket 42, which can be moved vertically by a movementdrive 41. In addition, the closing element 31 is rotatable around itslongitudinal axis I by means of a rotary drive 43.

To allow the pourable material to be easily supplied to the tap hole 14,a filling funnel 45 is attached to the main body 39 of the closingelement 31. There is also a supply 44 for repair compounds such as agunning compound T.

The head 37 of the closing element 31 is designed as an exchangeablepart. In the embodiment shown on the right side of the drawing, the base35 is slanted, while walls 36 of the groove 33 run axis-parallel to thelongitudinal axis I. In the embodiment shown on the left side of thedrawing, the base 35 is adjusted to the current state of the entrance 15of the refractory lining 17 of the tap hole 14. The walls 36 also runaxis-parallel to the longitudinal axis I.

FIG. 2 shows the compressible material F between the two bases 35 andthe respective entrance segments 15. The compressible material F isshown in the deformed state, in which it forms a tight seal between themolten metal melt M and the tap hole 14.

In FIG. 2, the mouth 16 of the tap hole 14 can be closed by a cut-offdevice 20, here, a slider 22.

In FIG. 2, the internal diameter d_(i) of the closing element 31 issmaller than the internal diameter D_(i) of the tap hole 14.

FIG. 3 shows the main body 39 of closing element 31 and the exchangeablepart 37 attached thereto via a detachable connection 38. In theembodiment shown in the left half of the drawing, the groove 33 has abase 35 arranged at a right angle to the main axis I. The groove 33 alsohas walls 36, which are embodied on the left side as a compensator andon the right side, for example, from paperboard. In the interior 34 ofthe groove 33, there is compressible material F. An empty space, inwhich gas can collect, remains, reaching to the mouth of the walls 36.The gas G is collected from a liquid or solid medium H after itstransition into the gaseous phase due to heat. In the preferredembodiments, the walls 26 have a thickness of 0.3 to 20 mm.

On the embodiment shown on the right side of the drawing, the base 35 ofthe groove 33 with the walls 36 is slanted. The compressible material F,embodied as a formed piece, is placed in front of this slanted base 35.A gas G can be conveyed to the groove 33 via a boring through the mainbody 39 and the exchangeable part 37.

We claim:
 1. A process for closing a tap hole in the bottom of ametallurgical vessel that is filled with a metal melt with a verticallymovable tubular closing element and with a cut-off device below thevessel bottom, comprising the steps of:placing a fire-resistant materialon a mouth of the closing element; passing the mouth of the closingelement through the metal melt; providing a quantity of a medium on afront the fire-resistant material for substantially preventing contactbetween the fire-resistant material and the metal melt when the closingdevice is passed through the metal melt; compressing the mouth of theclosing element against the bottom of the metallurgical vessel therebyproviding a seal between the metal melt and the tap hole; and moving acut-off device in front of a bottom of the tap hole thereby allowing thetap hole to be filled with a pourable refractory compound via thetubular closing element.
 2. The process of claim 1, further comprisingthe step of rotating the tubular closing element about its central axisafter said step of compressing the mouth of the closing element againstthe bottom of the metallurgical vessel.
 3. The process of claim 1,wherein said step of providing a quantity of a medium comprisesproviding a quantity of a gas medium.
 4. The process of claim 1, whereinsaid step of providing a quantity of a medium comprises providing aquantity of nitrogen.
 5. The process of claim 3, wherein said step ofpassing the mouth of the closing element comprises passing the mouth andthe gas medium through the metal melt.
 6. The process of claim 1,wherein said step of providing a quantity of a medium comprisesproviding a quantity of one of a liquid and solid material thattransforms into a gaseous phase and creating a gas when the closingelement is passed through the metal melt; andsaid step of passing themouth of the closing element through the metal melt comprises passingthe mouth of the closing element through the metal melt wherein said gaslies protectively in front of the fire-resistant material.
 7. A devicefor closing a tap hole in the bottom of a metallurgical vessel,comprising:a tubular closing element vertically movably mounted in saidmetallurgical vessel and having a lower end and an upper end; a forkedgroove having a blind end and an open end mounted at the bottom end ofsaid tubular closing element, said open end facing the bottom of thevessel; a compressible material arranged at the blind end of saidgroove; a gas occupying a space in said groove between said compressiblematerial and said open end; said forked groove comprising flexible wallswhich provide insubstantial resistance to the advancement of the closingelement toward the bottom of the metallurgical vessel such that saidcompressible material contacts the vessel bottom and creates a sealbetween the metal melt surrounding said closing element and the tap holebelow said closing element when said closing element is in a fullylowered position; and a cut-off device for shutting the tap hole of themetallurgical vessel from the outside of the vessel.
 8. The device ofclaim 7, wherein said flexible walls comprise metal compensators.
 9. Thedevice of claim 8, wherein said walls comprise a thickness in the rangeof 0.3 to 20.0 mm and said walls comprise a metal that softens whenexposed to the heat of the metal melt in the vessel.
 10. The device ofclaim 7, further comprising an exchangeable head part exchangeablyconnected between the tubular closing element and the groove such thatthe head and groove are exchangeable as one piece.
 11. The device ofclaim 10, wherein said tubular closing element comprises a first wallthickness and said head part comprises a second wall thickness whereinsaid second wall thickness is in the range of 3 to 10 times the firstwall thickness.
 12. The device of claim 11, wherein a ratio of theinternal diameter of the closing element d_(I) to the internal diameterof the tap hole D_(I), d_(I) /D_(I), is in the range of 0.7 to 2.0. 13.The device of claim 7, wherein said compressible material comprises afire-resistant material.
 14. The device of claim 7, wherein said blindend of said groove is conically inclined toward a longitudinal axis ofthe closing element.
 15. The device of claim 7, wherein said blind endcomprises a shape corresponding to that of an entrance to said tap hole.